Manufacture of metal nitrates



3, 1952 T. CRITCHLEY 2,581,519

MANUFACTURE OF METAL NITRATES Filed Feb. 17, 1948 2 SHEETS-Sl-IEET l Thomas 6r/7c/7/ey By his affomeys J n- 952 T. CRITCHLEY MANUFACTURE OF METAL NITRATES 2 SHEETS-SHEET 2 Filed Feb. 17, 1948 mum/0r 7/70/7705 Cr/fch/ By his aI/omeys Patented Jan. 8, 1952 UNITED MANUFACTURE OF MnTAnN TRA'rES Thomas Critchley, Brimsdown, Enfield', -England, assignor to Johnson & Sons smelting Works Limited, Enfield, England, av British company Application February 17, 1943, Serial N6. 8,825 In Great Britain March 8, 1946 This invention relates to improvements in and relating to the manufacture of metal nitrates by the reaction of nitric acid with a metal, such as silver or bismuth. One object of the invention is toprovide an improved method of carrying out'the reaction which is simple tooperate and moreeconomical than existing methods.

A further object is to provide a method by which substantially the whole of the nitric acid is utilised in the reaction to form the nitrate of the metal and to-enable a relatively low acidity nitrate to be obtained. I

A still further object is to provide a method whereby the reaction takes place in an; atmosphere of oxygen ora gas consisting mainly of oxygen. l a 1 Another object is to enable thereaction to take place initiallyover alocalised portion of the surface of a column of metal and, to maintain the acid in contact with said surface portion fora time suflicient to allow of substantially the whole reaction to take place thereat.

In my co-pending applications :Serial Nos 8,823 and 8,824, filed February 17, 1948, the latter now abandoned, I have disclosed respectively a process for the disposal of fumes of nitrogen oxides evolved during a chemical reaction and a process for the manufacture of silver or bismuth nitrate. 1

The present application is concerned solely with a method of obtaining maximum utiliza tion of the acid, particularly in cases where the metal to be reacted is in the form of a column of bars and has for its purpose to delay the passage of the acid over the bars for a predetermined time, so as to ensure a period of contact of the acid with the metal comparable to that obtainable when a column of granular or nodular metal is used. The process is applicable for use with any metal which, on reaction with nitric acid, gives rise to the evolution of the higher oxides of nitrogen. l

In its broadest aspect, therefore, my improved. process of manufacturing a metal nitrate com: prises essentially causing the reaction to take place in an atmosphere of oxygen or a gas consisting mainly of oxygen initially over a localised portion of the surface, of a column of metal and so regulating the supply of acid to and the flow: thereof over the column that substantially the whole of the introduced acid reacts with the metal to form the nitrate of the metal during the said initial reaction, any acid, remaining unutilised, being subsequently substantially wholly 3 Claims. (61. s nim 56 pipe IT is located beneath the tube l3 leading to utilised to form additional nitrate and collecting the nitrate solution formed as a result of the re-:

action. L l

A yet'fu'rther object of the invention is to provide a novel arrangement of apparatus for carrying out myimproved method which is of simple construction and occupies the minimum of space.

Themanherin which the above and other objects are attained will be more readily understood by reference to the following detail description taken in conjunction with the accompanying diagrammatic drawings, of which Figure 1 is a sectional elevation of apparatus constructed in accordance with my invention for carrying out my improved process of manufacturing a metal nitrate, and t Figure 2 shows the apparatus of Figure 1 in association with apparatus for recovering, in theform of nitric acid, any oxides of nitrogen which may not have been regenerated during the reaction.

Referring now to the drawing, and first to Figure 1 thereof, th apparatuscomprises a tubular reaction tower l of stainless steel formed of an upper portion 2 and a lower portion 2a bolted together at 2b. The lower portion 2a is formed with a ledge 20, supporting a perforated or meshed disc 3 on which rest bars 4 of metal, in this instance, silver. Secured to the lower end of the reaction tower I is a conical extension 5, pro

vided with a tap 6. The lower portion 2a of the tower I is surrounded for a portion of its length by a heating jacket 7, which may be heated in 8 is provided with a charging opening 811 and a.

further opening 81) through which pass a pipe It! for the supply of nitric acid and a pipe II for thesupply of oxygen. An outlet pipe l2 also leads from apoint adjacent the lower end of the portion 2a of the tower and is formed with a rising portionlZq, the height of, which is determined by theheight of liquid in the tower and enters the upper end of an auxiliary tube I 3 containing a lower layer of inert material I4, and

an upper layer of granulated silver I5, supported on a perforated plate [6. A depending outlet An outlet 9 is provided adjacent a collecting vessel I8 for the silver nitrate formed, which is withdrawn through the outlet I9. A pipe 20 for the supply of oxygen to the tube I3 is located in the side of the pipe IT. The tube I3 is surrounded by a water jacket 2 I, heated in any suitable manner, such as steam or a thermostatically controlled immersion heater. A pipe 22 leads from the top of the tube I3 to the upper tower portion 2.

In the use of the apparatus for the manufacture of silver nitrate, the lower portion 2a of the tower I is first filled with bars of silver 4, the upper portion 2 is then bolted in place and further bars inserted. A cold silver nitrate solution 4a is then introduced until it overflows through the pipe I2 into the tube I3 and so as partly to immerse the silver bars 4. The cover 8 is then fitted in place.

The reaction tower I and the auxiliary tube I3 are .now initially heated to a temperature of about 80 C. and during this time, oxygen is admitted to the tower I and the tube I3 to expel all air therefrom. Nitric acid of suitable specific gravity e. g. 1.25-1.30 is then introduced through the pipe ID, at the rate of 280 cc./hr./sq. inlof surface area of the base of the column and, by the impingement thereon of the entering oxygen, is formed into a spray.

The nitric acid, in the presence of the oxygen, comes initially into contact with the silver bars adjacent the surface of'the nitrate solution 4a and reacts with the metal to form silver nitrate solution. The continuous formation of this freshnitrate solution, adjacent the surface of the liquid in the tower I, forces this liquid out of the tower I and along the outlet pipe i2 leading therefrom and up the rising portion I2a of the pipe l2 from which it is delivered to the auxiliarytube I3. The nitratesolution formed by the aforesaid reactiontogether with any unreacted nitric acid is thus continually forced gradually downwardly by the fresh nitrate con tinually being formed adjacent the surface of the solution in the tower I and passes over the whole of the column of silver 4 and out through the said outlet pipe I2, any unreacted acid being thereby substantially entirely converted to the nitrate before reaching the end of the column. After the reaction has proceeded for some time, all the nitrate solution originally surrounding the metal bars will have been displaced and the solution flowing into the tube I3 will then consist substantially entirely of silver nitrate solution formed as a result of the reaction. Any nitric acid, which may have been regenerated from the nitrogen oxide fumes evolved,

. will mix with the freshly entering nitric acid at the upper end of the column and react therewith on the metal.

the oxygen to nitric acid, will act on the granulated silver in the tube I3 to form additional nitrate.

In this Way substantially the whole of the acid is utilised in the reaction and a concentrated relatively low. acidityv nitrate solution is collected in the collecting vessel I8.

Any brown fumes of oxides of nitrogen evolved during-the reaction and which have not been reconverted to nitric acid in the tower I and which issue through the outlet 9 at the upper end of the said tower I may, as stated above, be disposed of in any suitable known manner, but are preferably treated in the manner shown in Figure 2, to which reference is now directed.

In this figure the reaction tower I and associated partsv are similar to those shown in Figure l and similar reference numerals are 9 adjacent the ,upper end of the reaction tower;

The absorption tower 23 is partly filled with an inert material 23 such as quartz A pipe 29 is provided in the conduit, 27 foradmittingdistilled water tothe tower 23.; The bottom of the absorption tower 23 is inwardly flanged at 30' to provide an aperture 3|, opening to a tubular extension 32, projecting into a collecting vessel 33, provided with an overflow pipe 34. The said aperture 3I iscovered by a perforated or meshed disc 35 on which rests the inert material 28.

7 From the interior of the tubular extension 32, above the collecting vessel 33 extends a pipe 36 leading to a manometer 31, the end of which pipe 36 is immersed in waterin the manometer 31, which is open to the atmosphere at 38.

The absorption tower 23 issurrounded by a cooling'jacket 39 through which cold 'water is circulated. V

It Will now be assumed that the reaction described above is being carried out in the reaction tower I. Any oxides of nitrogen evolved during the reaction in the reaction tower I and not reconverted therein to nitric acid will pass through the aforesaid conduit 21 into the absorption tower 23, where, mixed with distilled water, entering through thepipe 29; theyjpass over the quartz 28. The supply of oxygen to the reaction tower I is regulatedso that only an occasional bubble passesthrou'gh the manometerll. The mixture of oxides of nitrogen, oxygen and water are thus convertedintonitric acid which collects in the collecting vessel 33 and is withdrawn through the aforesaid overflow pipe 34 If desired, the nitric acid obtained may be mixed with concentrated nitric acid to provide a solution having the required specific gravity for subsequent utilisation'in'the reaction tow'er.

Whilst, in the above,aspecific embodiment of the invention has been described by way of example, it will be understood by those skilled in the art that modifications may bemade therein withoutdeparting-from the spirit and scope of the inv tntion, as defined by the appended claims.

What I claim is: v V

r 1. A proces's for the manufacture of a metal nitrate by reaction of nitric acidon a metal giving rise" to thef evolution of the higher oxides of nitrogen, which process comprises immersing a column of the selected metal at least partlyin a solution of the nitrate of said'metalmaintained at a predetermined height surroundin and displaceabl from mm column, continuously bringing a film of nitric acid at a regulated rate into column to cause reaction of said acid with said metal with continuous formation of nitrate solution and constant evolution of a regulated amount of nitrogen oxide fumes, simultaneously continuously introducing to said reaction zone oxygen gas at a rate' sufficient to replace the oxygen used in converting the evolved nitrogen oxides directly to nitric acid and to maintain the pressure in the 1 reaction zone substantially constant, causing said reconvertednitric acid to react with said metal to increase the concentration of the nitrate solution, and continuously removing the nitrate solu tion as additional nitrate solution is formed;

2. The process claimed in claim 1 including the additional step of forming the entering nitric acid into a spray by impinging thereon of the stream of oxygen gas.

3. The process according to claim 1 including the additional step of bringing the removed nitrate solution into intimate contact with a stream of oxygen gas to remove any traces of free nitrous acid from said solution.

THOMAS CRITCHLEY. ll

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,013,984 Bosch et a1 Jan. 9, 1912 1,180,964 Auger Apr. 25, 1916 1,247,280 Keller Nov. 20, 1917 2,053,518 Crittenden Sept. 8, 1936 2,062,091 Gooch Nov. 24, 1936 2,072,947 Folger Mar. 9, 1937 2,206,495 Beardsley July 2, 1940 FOREIGN PATENTS Number Country Date 188,868 Great Britain Nov. 23, 1922 413,721 Great Britain July 11, 1934 OTHER REFERENCES Mellor, Inorganic and Theoretical Chemistry, vol. 3, p. 459, London, Longmans, Green and 00., 1923.

Chemical and Metallurgical Engineering, vol. 53, No. 8 (August, 1946), pages 113415. 

1. A PROCESS FOR THE MANUFACTURE OF A METAL NITRATE BY REACTION OF NITRIC ACID ON THE METAL GIVING RISE TO THE EVOLUTION OF THE HIGHER OXIDES OF NITROGEN, WHICH PROCESS COMPRISES IMMERSING A COLUMN OF THE SELECTED METAL AT LEAST PARTLY IN A SOLUTION OF THE NITRATE OF SAID METAL MAINTAINED AT A PREDETERMINED HEIGHT SURROUNDING AND DISPLACEABLE FROM SAID COLUMN, CONTINUOUSLY BRINGING A FILM OF NITRIC ACID AT A REGULATED RATE INTO CONTACT WITH THE UPPER PORTION OF SAID METAL COLUMN TO CAUSE REACTION OF SAID ACID WITH SAID METAL WITH CONTINUOUS FORMATION OF NITRATE SOLUTION AND CONSTANT EVOLUTION OF A REGULATED AMOUNT OF NITROGEN OXIDE FUMES, SIMULTANEOUSLY CONTINUOUSLY INTRODUCING TO SAID REACTION ZONE OXYGEN GAS AT A RATE SUFFICIENT TO REPLACE THE OXYGEN USED IN CONVERTING THE EVOLVED NITROGEN OXIDES DIRECTLY TO NITRIC ACID AND TO MAINTAIN THE PRESSURE IN THE REACTION ZONE SUBSTANTIALLY CONSTANT, CAUSING SAID RECONVERTED NITRIC ACID TO REACT WITH SAID METAL TO INCREASE THE CONCENTRATION OF THE NITRATE SOLUTION, AND CONTINUOUSLY REMOVING THE NITRATE SOLUTION AS ADDITIONAL NITRATE SOLUTION IS FORMED. 